1. Technical Field
The disclosure relates to an ink circulation type inkjet printer.
2. Related Art
Japanese Unexamined Patent Application Publication No. 2008-162262 describes an ink circulation type inkjet printer that performs printing by ejecting ink through a nozzle of an inkjet head while circulating the ink.
In some ink circulation type inkjet printers, a positive pressure tank is disposed upstream of an inkjet head, a negative pressure tank is disposed downstream of the inkjet head, the positive pressure tank is disposed at a position higher than the inkjet head, and the negative pressure tank is connected to an air pump for generating a negative pressure.
Such an inkjet printer circulates ink and generates a negative pressure appropriate for ejection of ink in a nozzle, by using a hydraulic head pressure (positive pressure) caused by the difference in height between the positive pressure tank and the inkjet head, and by using a negative pressure generated in the negative pressure tank by the air pump.
In an inkjet head in which nozzles are disposed in a high density to achieve printing in a high resolution, a flow path of ink is narrow, and accordingly a flow path resistance is high. When such an inkjet head is used in an inkjet head printer in the above-described configuration, the difference in height between the positive pressure tank and the inkjet head has to be large in order to obtain a needed circulation flow rate. This may result in an increase in the size of the printer.
If an air pump generates a pressure (positive pressure) also in the positive pressure tank, a needed pressure may be generated regardless of the difference in height between the positive pressure tank and the inkjet head. However, the provision of separate air pumps to the positive and negative pressure tanks causes the size and cost of the printer to increase.
To address this issue, there is provided a printer in which a single air pump sucks air from the negative pressure tank and delivers air to the positive pressure tank, thereby generating a positive pressure in the positive pressure tank as well as a negative pressure in the negative pressure tank.